1. Field of the Invention
This invention relates to a camera using film with a magnetic memorizing portion and provided with writing instruction means for driving a magnetic head during the feeding of the film by film feeding means after the termination of photographing, and causing camera information to be overwritten on film information pre-written in the magnetic memorizing portion of an exposed frame.
2. Description of the Related Art
A camera using a film cartridge containing the leading end portion of film therein and rewinding film that has not been completely exposed (halfway removal) and the reloading and use of the film cartridge is disclosed in U.S. Pat. No. 4,878,075.
In this patent, there are disclosed the technical substance that the film is provided with a magnetic memorizing portion comprising a transparent magnetic layer, that the camera has a magnetic head for writing information into the magnetic memorizing portion or reading out information pre-recorded in the magnetic memorizing portion, and that in order to discriminate between exposed and unexposed frames when the film in the cartridge has been rewound without completely exposing all of the film frames is again reloaded,
1) particular information is recorded on an exposed frame and this is used as an exposed flag (hereinafter referred to as DEP flag (Double Exposure Prevention encodement)) and whether there is this DEP flag during reloading is read out by the magnetic head, and a frame having this DEP flag is judged to be an "exposed" frame, and
2) film information is pre-recorded on the film and the camera makes or generates the DEP flag by overwriting particular information on an exposed frame or simply erasing the film information, and whether the DEP flag 1 is present during reloading is read out by the magnetic head, and a frame having this DEP flag is judged to be an "exposed" frame.
In the above-mentioned patent, there is further disclosed the sequence of film winding.fwdarw.exposed frame detection.fwdarw.unexposed frame positioning during reloading.
Further, in W090/04204, film information pre-recorded on film by a film maker and camera information recorded on each frame by a camera are prescribed as being comprised of an information block called "N bits of ID sentinels+data characters", and different ID sentinels are prescribed for the purpose of distinguishing between the camera information and the film information and the purpose of detecting a start sentinel. Also, it is disclosed that the ID sentinel of the camera information differing from the film information is used as DEP flag.
However, both of the above-described examples of the related art are designed such that "exposed" frames are discriminated by the presence of DEP flag, and this has led to the following serious problems:
1) Since there is only a single DEP flag in each photographing frame, a very low reproduction error rate is required in order to detect this DEP flag; and
2) When one fails in detecting the DEP flag, due to a reproduction error, an "exposed" frame is discriminated as unexposed, and double exposure takes place.